Implantable stimulators such as cardiac and nerve stimulators typically include a pulse generator component and a lead system that is connectable to the pulse generator component. The lead system may include one or more lead wires that plug in to the pulse generator component, and have one or more electrodes provided at a distal portion of the lead. Such implantable stimulators may provide stimulation to cardiac or other tissue such as nerves, as needed. In the case of cardiac stimulation, therapy may be provided in the form of pacing, cardioversion, and defibrillation pulses.
Various forms of pressure sensors are available for monitoring pressure within a living being. In addition, in the case of implantable defibrillators, it has long been believed that one way to assess whether or not to deliver a defibrillation pulse is to monitor an intracardiac pressure signal (that is, a pressure signal measured from within a chamber of the heart, such as inside the ventricle). It has proven challenging, however, to provide a viable cardiac stimulation system that enables accurate monitoring of intracardiac pressure signals, while also providing for the sensing and stimulation electrodes that are necessary in such a system. Commercial implantable defibrillator systems, for example, uniformly assess cardiac electrical information in determining if and when a defibrillation pulse should be delivered to a patient, as opposed to measuring intracardiac pressure. One reason this may be the case is that the same electrodes used for delivery of stimulation pulses are used for sensing.
Implantable stimulators may benefit from further information to analyze to determine, or confirm, that a patient is indeed in a dangerous state where a painful electrical pulse should be delivered. For example, unnecessary shocks are problematic in implantable defibrillator systems, because the shocks may be very painful to the patient.